#include <stdio.h>
 int main()
 {
  char P[100];
  char C[100];
  int K=3,i;
  printf("Please input Plaintext:\n"); 
  gets(P); 
    for(i=0;P[i]!='\0';i++)
 {  
  if(P[i]>='a'&&P[i]<='z') 
  C[i]=(P[i]-'a'+K)%26+'a';
  else if(P[i]>='A'&&P[i]<='Z')
  C[i]=(P[i]-'A'+K)%26+'A';
  else C[i]=' ';
  } 
  printf("The Ciphertext is :\n%s\n",C);
  getch();
  return 0;
} 
